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De Dion tube failure - a word to the wise


don_g

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My venerable De Dion tube failed at Brands last week - fortunately without any damage at all to me or the car. The tube is ancient but, as those of you who know how I drive will agree, rarely subject to much stress. It was also crack tested prior to Le Sept, showed no rust or polishing along the fracture line and was rarely kerbed, indicating a pretty sudden failure.

 

If it does go you'll get no more than a couple of hard corners worth of warning. If you can't put the changes in handling down to oil, wet, etc retreat to the pits and explore! On my return to the pits there was less than one inch of intact tube remaining! And the negative camber on the 'failed' side was around 30 degrees!

 

The new ones are thicker (10 gauge), heavier and shouldn't fail (!). But check 'em!

 

P.S Gary May (he of Juno Sportscars and Freestyle fame) provided a spare and we fitted it at the track. Thanks to Gary (diamond guy) and the apprentices!

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The newer ones have a much longer / stronger strengthening triangulation. These however seem to fail at the weld for the progressive springs and damper mounts.

The old through the tube damper mount is probably stronger. My tube has both types of mounting point. I guess they all do.

 

Interesting about the camber increase and how it feels as it goes.... A Sierra in front of me at Brands on Saturday had his left rear dissappear into the wheel arch. Following him on the warm up lap for qualifying I could see he had problems getting the power down out of Clarke curve, then the left started smoking then cambered up massively and he was avoided rapidly.

 

Steve

My racing pics, 7 DIY, race prep. Updated often here

Hants (North) and Berkshire area club site

here

 

 

Edited by - stevefoster on 20 Aug 2002 11:22:17

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same thing happened to our nurburgring 24hour car.. luckily with enough time to swap it.. but it went in exactly the same place.

 

it was said to be terrifying when it happened.. the car "snapped" sideways in the middle of bigger and quicker traffic, on the nordschleife.

 

all's well that ended well though, as my forthcoming feature in low flying will detail.

 

PLUG ! PLUG ! 😬

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I know of 3 variations of de dion tube (having used all of them !)

Original design (circa 1990)

Original design but in heavier gauge material

Wide Butress design (the bit that the a frame connects to) and heavier gauge "race" tube.

There could be more !

The Wide butress type requires (on my 1990 chassis) that the chassis tube (in the area of the a frame bush) is flattened off to clear the de dion tube.

 

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